I don't know how to change the ink - Canon PIXMA MP240 All-In-One InkJet Printer

With the printer facing you, open the scanning unit cover by pulling upwards until it locks into place leaving the top of the printer accessible.

If you dont know what the "scanning unit cover" is, let me help you locate it. Look at the place where your paper comes out after printing. It should be straight down and in front of you if your standing in front of the printer. Right above the paper tray, is the plastic top of the printer which is called the "scanning unit cover". Put your finger under the cover and lift upward. The top should lift easily. Pull upward until it locks and remains open exposing the inside of your printer.

When the cover opens and locks it will automatically trigger the carriage which holds the printer cartridges to move to the center and stop.

Put your finger under the plastic tab on top of the cartridge that you want to change and pull upwards to release it. Pull the cartridge out, open the new one and remove the tape to open the ink flow. Put the cartridge in and push it down and close it into place.

Close the scanning unit cover and watch the digital read out on the printer to see if you installed the cartridge correctly. If you did, the printer will recognize the new ink cartridge and tell you to print a test page to align the print heads. When the alignment page prints you are finished and your printer is ready to go.

Grab a manual at LINK.